A machining liquid must flow over a part of a metal workpiece being machined when machining the metal workpiece by a machine tool using a tool to ensure a satisfactory cooling action to remove heat generated in the part of the workpiece being machined and to promote a smooth cutting action of the tool by removing chips.
A conventional machining liquid supply system employed in a conventional machine tool is disclosed e.g., in Japanese Unexamined Utility Model Publication (Kokai) No. 61-124366. The system is of a manually operated type having a machining liquid spouting nozzle disposed in alignment with a tangent to a grinding wheel at a grinding point and supported on a wheel guard so as to be movable in directions perpendicular to the same tangent to the grinding wheel. When using this prior art machining liquid supply system, the operator operates an adjusting handle to locate the machining liquid spouting nozzle in a predetermined positional relation with the grinding wheel regardless of the change of the diameter of the grinding wheel so that a machining liquid is spouted in a direction tangential to the grinding wheel at the grinding point. The conventional machining liquid supply system, however, is not perfectly satisfactory because, when the grinding point is changed during a grinding process, the machining liquid supply system is unable to spout the machining liquid in a direction tangential to the grinding wheel at a new grinding point.
A machining liquid spouting method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 1-146662 has a machining liquid spouting nozzle capable of being turned for indexing about a spindle holding a grinding wheel during a contour grinding process, and controls the position of the machining liquid spouting nozzle relative to a grinding point according to a grinding wheel moving program for the contour grinding process. This conventional machining liquid spouting method, however, turns the machining liquid spouting nozzle about the spindle to adjust machining liquid spouting direction when the grinding point where the grinding wheel grinds a workpiece is displaced, but does not move the machining liquid spouting nozzle radially relative to the center of the grinding wheel. Thus, the conventional method of this prior art teaches nothing about a method of adjusting the machining liquid spouting direction of the machining liquid spouting nozzle when a grinding wheel of a different diameter is mounted on the spindle.
A water spouting system for a machining center, disclosed in Japanese Unexamined Patent Publication (Kokai) No. 6-31582 is capable of optionally spouting water through a water spouting nozzle either in a horizontal direction or a vertical direction toward a machining point where a tool of the machining center cuts a workpiece so that water can always be spouted toward the machining point. In this prior art water spouting system, the water spouting nozzle can be moved by a gearing about a spindle holding a tool, the water spouting nozzle is moved in a moving angle when the machining point moves horizontally so that the water spouting nozzle is able to spout water toward the machining point. The water spouting nozzle is turned about its base end to move the tip thereof vertically when the height of the machining point changes in order that the water is spouted exactly toward the machining point.
Since the water spouting nozzle of the prior art water spouting system for a machining center cannot be moved radially with respect to the center of the tool held on the spindle, the water spouting direction of the water spouting nozzle cannot sufficiently correctly be adjusted with respect to the machining point when the diameter of the tool changes.
A grinding machine provided with a wheel guard for covering a grinding wheel is disclosed in U.S. Pat. No. 4,619,078. In this known grinding machine, a grinding wheel held on a spindle is covered with a wheel guard, and a machining liquid spouting nozzle is held on the wheel guard so as to be able to turn together with the wheel guard about the spindle and to be able to be moved radially with respect to the spindle according to the diameter of the grinding wheel. The machining liquid spouting nozzle is turned together with the wheel guard so that a machining liquid can be spouted into a machining region in which the grinding wheel grinds a workpiece and the wheel guard may not interfere with the workpiece.
The known grinding machine is a special machine tool, such as a surface grinder, and the wheel guard for covering the grinding wheel is an essential component. Therefore, if an automatic tool changer is used to mount a tool detachably on the spindle, the tool changing operation of the automatic tool changer is interfered with by the wheel guard and hence the automatic tool changing operation cannot be achieved. Furthermore, the known grinding machine does not have any axis about which the workpiece is rotated, and the workpiece can be fed only linearly along three axes, i.e., an X-, a Y- and a Z-axis. Consequently, some workpieces of a particular shape interfere unavoidably with the wheel guard or the machining liquid cannot be properly spouted into the machining region if the interference between the workpiece and the wheel guard is avoided. The known grinding machine is not provided with any measuring means for measuring the diameter of the grinding wheel, and nothing is disclosed with regard to techniques of automatically adjusting the radial position of the machining liquid spouting nozzle relative to the grinding wheel on the basis of measurement of the diameter of the grinding wheel when the grinding wheel is abraded or the diameter of the grinding wheel is changed by dressing or truing.